Semiconductor laser with two active layers

Abstract

In a semiconductor laser, a laminated multi-layer body is on a prescribed region of the surface of a semiconductor substrate of first conductivity type, and a burying laminated layer body surrounds the laminated layer body in contact with the lateral wall thereof. The laminated layer body includes a first cladding layer having the first conductivity type, a first active layer, a second cladding layer having the opposite conductivity type (second conductivity type) to that of the semiconductor substrate, a second active layer and a third cladding layer of the first conductivity type. The burying laminated layer body includes a semiconductor electrode layer of the second conductivity type and low specific resistivity which substantially contacts the second cladding layer, and two groups of burying layers respectively provided on the prescribed regions of the top and bottom surface of said semiconductor electrode layer. When a prescribed amount of direct current is supplied to a first electrode mounted on the upper side of the laminated layer body, a second electrode deposited on the bottom side of said laminated layer body and a third electrode set on the semiconductor electrode layer included in the burying layer body, then the first and second active layers arranged very close to each other simultaneously oscillate two independent laser beams admitting of modulation with a low threshold current value.

What we claim is: 
     
       1. A semiconductor laser which comprises: a semiconductor substrate of a first conductivity type;   a laminated layer body comprising a first cladding layer of the first conductivity type, a first active layer, a second cladding layer of a second conductivity type opposite to said first conductivity type, a second active layer and a third cladding layer of the first conductivity type all laminated in the order mentioned on a prescribed region of the surface of said semiconductor substrate as counted from said surface, both of the end surfaces of said laminated layer body comprising mirrors to form a resonant cavity;   a burying laminated layer body which is formed on the semiconductor substrate so as to surround and contact with said laminated layer body, said burying laminated layer body comprising a first burying layer, a semiconductor electrode layer of the second conductivity type and a second burying layer all laminated in the order mentioned as counted from said semiconductor substrate;   said semiconductor electrode layer substantially contacting said second cladding layer to provide a current path for a current flowing from a third electrode to said second cladding layer, and said semiconductor electrode layer having a low specific resistivity;   a first electrode coupled to said third cladding layer;   a second electrode coupled to said semiconductor substrate;   said third electrode being coupled to said semiconductor electrode layer; and   power supply means including a first power source coupled between said first and third electrodes, and a second power source coupled between said second and third electrodes.   
     
     
       2. A semiconductor laser which comprises: a laminated layer body which is mounted on a prescribed region of the surface of a semiconductor substrate of a first conductivity type, said laminated layer body comprising a first cladding layer of the first conducitivity type, a first active layer, a second cladding layer of a second conductivity type opposite to the first conductivity type, a second active layer and a third cladding layer of the first conductivity type all laminated in the order mentioned as counted from said surface of said semiconductor substrate, both of the end surfaces of said laminated layer body comprising mirrors to form a resonant cavity;   a burying laminated layer body which surrounds and contacts with said laminated body, said burying laminated layer body comprising a first burying layer, a semiconductor electrode layer of a second conductivity type and a second burying layer all laminated on said surface of said semiconductor substrate in the order mentioned as counted from said surface;   said semiconductor electrode layer contacting said second cladding layer to provide a current path for a current flowing from a third electrode to said second cladding layer;   said first burying layer contacting said first cladding layer and said first active layer;   said second burying layer contacting said second active layer and said third cladding layer;   a first electrode coupled to said third cladding layer;   a second electrode coupled to said semiconductor substrate;   said third electrode being coupled to said semiconductor electrode layer; and   power supply means including a first power source coupled between said first and third electrodes, and a second power source coupled between said second and third electrodes.   
     
     
       3. The semiconductor laser according to claim 1 or 2, wherein said semiconductor electrode layer has a smaller refractive index than said first and second active layers. 
     
     
       4. The semiconductor laser according to claim 3, wherein said semiconductor electrode layer has a wider forbidden band gap than said first and second active layers. 
     
     
       5. The semiconductor laser according to claim 1 or 2, wherein said first and second active layers have a narrower forbidden band gap than said first to third cladding layers and first and second burying layers; and said first and second active layers have a larger refractive index than said first to third cladding layers and first and second burying layers. 
     
     
       6. The semiconductor laser according to claim 1 or 2, wherein said first burying layer comprises a first semiconductor layer of the second conductivity type and a second semiconductor layer of the first conductivity type laminated on each other in the order mentioned as counted from said surface of said semiconductor substrate to jointly constitute a first PN junction; and   said second burying layer comprises a third semiconductor layer of the first conductivity type and a fourth semiconductory layer of the second conductivity type laminated on each other in the order mentioned as counted from the surface of the semiconductor substrate to jointly constitute a second PN junction.   
     
     
       7. The semiconductor laser according to claim 1 or 2, wherein said first and second burying layers each comprise at least one semiconductor layer of high resistivity. 
     
     
       8. The semiconductor laser according to claim 1 or 2, wherein said first and second active layers have different chemical compositions. 
     
     
       9. The semiconductor laser according to claim 1 or 2, wherein said first and second active layers have the same chemical composition. 
     
     
       10. The semiconductor laser according to claim 1 or 2, wherein said semiconductor substrate is a semiconductor containing any of the compounds belonging to Groups III and V of the periodic Table. 
     
     
       11. The semiconductor laser according to claim 10, wherein said semiconductor is InP. 
     
     
       12. The semiconductor laser according to claim 10, wherein said semiconductor is GaAs. 
     
     
       13. The semiconductor laser according to claim 10, wherein said first to third cladding layers and said first and second burying layers are InP; and said first and second active layer are GaInAsP. 
     
     
       14. The semiconductor laser according to claim 13, wherein said semiconductor electrode layer is GaInAsP. 
     
     
       15. The semiconductor laser according to claim 13, wherein said semiconductor electrode is InP. 
     
     
       16. The semiconductor laser according to claim 11, wherein said first to third cladding layers and said first and second burying layers are GaAlAs; and said first and second active layers are GaAs. 
     
     
       17. The semiconductor laser according to claim 16, wherein said semiconductor electrode layer is GaAs. 
     
     
       18. The semiconductor laser according to claim 16, wherein said semiconductor electrode layer is GaAlAs. 
     
     
       19. The semiconductor laser according to claim 1 or 2, wherein said first electrode is mounted on said third cladding layer with a cap layer interposed therebetween.